Vapor deposition film and packaging material

ABSTRACT

A vapor deposition film comprises a substrate made of a plastic material, a primer layer made from a composition comprising a specific trifunctional organosilane or a hydrolysate of the organosilane, an acryl polyol and an isocyanate compound, and an inorganic oxide vapor deposition layer to a thickness of 5˜300 nm, formed by successive lamination on at least one side of the substrate. Also, packaging materials and packages which employ the film are provided.

This application claims 35 USC 371 priority from PCT/JP99/00848, filedFeb. 24, 1999 and 35 USC 119 priority from Japanese application10/235611, filed Aug. 21, 1998.

TECHNICAL FIELD

The present invention relates to a vapor deposition film with excellentadhesion of a vapor deposition layer and to a packaging material usingthe same, and more specifically relates to packaging materials used forpackaging in the fields of foods, non-foods, medicines and so forth, aswell as a vapor deposition film used for such packaging materials, andparticularly to packaging materials used in packaging fields whichrequire boiling sterilization, retort sterilization, autoclavesterilization and the like, and to a vapor deposition film used for suchpackaging materials.

BACKGROUND ART

In recent years packaging materials used for packaging of foods,non-foods, medicines, etc. must have the ability to block the effects ofoxygen, water vapor and other gases which permeate the packagingmaterials and alter the quality of their contents, in order to preventsuch alteration in the contents and maintain their functions andproperties. Hence there is a demand for packaging materials with gasbarrier properties which block these gases. Commonly used packagingmaterials to date have therefore employed metal foils of aluminum, etc.as gas barrier layers, because they are largely unaffected bytemperature and humidity.

Nevertheless, while packaging materials employing aluminum and othermetal foils have excellent gas barrier properties, problems have existedbecause of their drawbacks, which include the fact that such packagingmaterials are not transparent enough to allow visual verification oftheir contents, that they must be treated as non-combustibles whendisposed of after use, and that metal detectors cannot be used for theirexamination.

As packaging materials designed to overcome these drawbacks there havebeen developed films wherein silicon oxide, aluminum oxide, magnesiumoxide or another inorganic oxide vapor deposition film has formed on apolymer film by a forming means such as vacuum vapor deposition orsputtering, as is described, for example, in U.S. Pat. No. 3,442,686,Japanese Examined Patent Publication No. Sho 63-28017, etc. Such vapordeposition films are known to be transparent with gas barrier propertiesagainst oxygen, water vapor and the like, and are thus suitable aspackaging materials which provide both the transparency and gas barrierproperties which are unobtainable with metal foils, etc.

However, although such films are suitable for the packaging materialsdescribed above, virtually none of them can be used as vapor depositionfilms alone for packaging containers and packaging materials. This isbecause packages are completed by undergoing post-processing after vapordeposition, which involves various steps such as printing of charactersand images on the vapor deposition film surface, or attachment to otherfilms, etc. and shaping into packages for containers and the like. Inparticular, because packaging materials subjected to boilingsterilization, retort sterilization or autoclave sterilization aresterilized through many different steps, due care must be taken indesigning such packaging materials.

When attempts have been made to use these types of vapor depositionfilms in combination with sealant films to prepare bags which are thenfilled with contents and subjected to boiling sterilization or retortsterilization, peeling of the vapor deposition layer has occurred atparts of the sealed sections resulting in a poor outer appearance, whilethe gas barrier properties are also reduced at those sections, leadingto alteration in the quality of the contents.

In other words, the conditions for packaging materials in suchsituations include transparency which allows the contents to be directlyviewed, high gas barrier properties to block gases which adverselyaffect the contents, and resistance to sterilization treatment with nodeterioration of the gas barrier properties and no peeling after boilingsterilization, retort sterilization and autoclave sterilization; atpresent, however, no packaging materials have been discovered whichsatisfy all of these conditions. The conventional packaging materialshave also had the problem of deteriorating water resistance, andespecially poorer laminate strength after exposure to water.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a vapordeposition film which allows direct viewing of contents and which hashigh gas barrier properties comparable to those of aluminum foil. Inparticular, there is provided a vapor deposition film which exhibits nopeeling of the vapor deposition layer from the substrate ordeterioration of its gas barrier properties even after boilingsterilization or retort sterilization, and without loss of laminatestrength after exposure to water, thus promising a wide range ofpossible uses in packaging materials with general usefulness for foods,non-foods, medicines and the like.

It is a second object of the invention to provide a packaging materialmade using this vapor deposition film, which is a highly practicalpackaging material with high gas barrier properties and with highresistance to sterilization, undergoing no loss of its properties and nopeeling of the vapor deposition layer from the substrate even afterboiling sterilization or retort sterilization.

It is a third object of the invention to provide bag-like packages madeusing the packaging material, which are packages which undergo nodeterioration in oxygen permeability or laminate strength aftersterilization treatment, and which exhibit virtually no peeling of theirvapor deposition layers from their substrates.

In order to achieve the objects described above, the present inventionprovides a vapor deposition film comprising a substrate made of atransparent plastic material, a primer layer comprising a compositionwhich contains a trifunctional organosilane represented by the generalformula R′Si(OR)₃ (wherein R′ is a substituted or unsubstituted alkylgroup, vinyl group, etc. and R is an alkyl group, etc.) or a hydrolysateof the organosilane, an acryl polyol and an isocyanate compound, and avapor deposition layer comprising an inorganic oxide in a thickness of5˜300 nm, formed by successive lamination on at least one side of thesubstrate.

The present invention further provides the aforementioned vapordeposition film wherein R′ in the trifunctional organosilane is an alkylgroup including an epoxy group or isocyanate group.

A reaction catalyst is preferably added to the aforementionedcomposition for the primer layer. In particular, the reaction catalystmay be a tin compound, and is preferably a tin compound selected fromthe group consisting of tin chloride, tin oxychloride and tin alkoxides.

It is preferred to further add to the composition a metal alkoxiderepresented by the general formula M(OR)_(n) (wherein M is a metalelement, R is an alkyl group such as CH₃, C₂H₅, etc. and n is theoxidation number of the metal element) or a hydrolysate of the metalalkoxide. Here, the metal of the metal alkoxide is preferably a metalselected from the group consisting of Si, Al, Ti, Zr and their mixtures.

The thickness of the primer layer is preferred to be in the range of0.01˜2 μm.

The inorganic oxide of the vapor deposition layer is preferably oneselected from the group consisting of aluminum oxide, silicon oxide,magnesium oxide and their mixtures.

An overcoating layer may be also laminated on the vapor depositionlayer, and it is preferred for the overcoating layer to be a layerobtained by applying, heating and drying a coating agent composed mainlyof an aqueous solution or an aqueous/alcohol mixed solution containing awater-soluble polymer and either or both (a) at least one metal alkoxideor hydrolysate thereof and (b) tin chloride. Here, the metal alkoxide ispreferably one selected from the group consisting of tetraethoxysilane,triisopropoxyaluminum and mixtures thereof. The water-soluble polymer ispreferably polyvinyl alcohol.

The invention still further provides a packaging material prepared bylaminating the aforementioned vapor deposition film and a heat seallayer on the vapor deposition layer or the overcoating layer side.

The invention still further provides packages made into bag form usingthe aforementioned packaging material.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained in greater detail withreference to the drawings in which:

FIG. 1 is a partial cross-sectional view of a vapor deposition filmaccording to an embodiment of the present invention;

FIG. 2 is a partial cross-sectional view of a vapor deposition filmaccording to another embodiment of the present invention;

FIG. 3 is a partial cross-sectional view of a packaging materialprepared using a vapor deposition film according to yet anotherembodiment of the present invention; and

FIG. 4 is a perspective view of an embodiment of a package made usingthe packaging material shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 and FIG. 2 are cross-sectional views of vapor deposition filmsaccording to embodiments of the present invention.

In FIG. 1, the substrate 1 is a film made of a plastic material. On thesubstrate 1 there are successively laminated a primer layer 2 made of acomposition comprising a trifunctional organosilane, an acryl polyol andan isocyanate compound, and a vapor deposition layer 3 containing aninorganic oxide. In FIG. 2, an overcoating layer 4 is further laminatedthereon.

The substrate 1 is a plastic material, and a transparent film ispreferred to take advantage of the transparency of the vapor depositionlayer. As examples of substrates there may be mentioned polyester filmssuch as polyethylene terephthalate (PET) and polyethylene naphthalate;polyolefin films such as polyethylene and polypropylene; polystyrenefilms; polyamide films; polyvinyl chloride films; polycarbonate films;polyacrylonitrile films; and polyimide films. The substrate may bestretched or unstretched, and should have certain mechanicalstrength-and dimensional stability. Particularly preferred among theseare polyethylene terephthalate films optionally stretched in biaxialdirections. An opposite side of the substrate to the side thereof onwhich the vapor deposition layer is formed may also be coated withthin-films formed from any of various well known additives andstabilizers, including antistatic agents, ultraviolet inhibitors,plasticizers, lubricants and the like. For better adhesion with thesethin-films, the coated side of the substrate may be subjected to anytype of pretreatment, such as corona treatment, low-temperature plasmatreatment, ion bombardment treatment, chemical treatment, solventtreatment, etc.

The thickness of the substrate is not under any particular restrictions,and from the standpoint of suitability as packaging materials, the filmmay be laminated with a film of a different nature than the film itself.From the standpoint of workability when forming the primer layer andinorganic oxide vapor deposition layer, as well as the overcoatinglayer, a practical range of 3˜200 μm is preferred, with 6˜30 μm beingparticularly preferred.

From a productivity standpoint, a long, continuous film is preferredwhich allows continuous formation of each of the aforementioned layers.

The primer layer according to the present invention is formed on thesubstrate made of a plastic material, and this layer serves to increasethe adhesion between the substrate and the inorganic oxide vapordeposition layer, and to prevent peeling of the vapor deposition layerafter boiling sterilization, retort sterilization or autoclavesterilization.

As a result of much diligent research, the present inventors have foundthat compositions of trifunctional organosilanes or their hydrolysateswith acryl polyol and isocyanate compounds can be used as the primerlayer in order to achieve the aforementioned object of the presentinvention.

The composition of the primer layer will now be explained in detail.

The trifunctional organosilane used according to the present inventionis a compound represented by the general formula R′Si(OR)₃ (wherein R′is a substituted or unsubstituted alkyl group, vinyl group, etc. and Ris an alkyl group, etc.). Here, the substituent of R′ preferablyincludes an epoxy group or isocyanate group. As specific exemplarycompounds there may be mentioned ethyltrimethoxysilane andvinyltrimethoxysilane; glycidoxy propyltrimethoxysilane, glycidoxytrimethoxysilane and epoxycyclohexylethyl trimethoxysilane where R′includes an epoxy group; and γ-isocyanate propyltrimethoxysilane andγ-isocyanate propyltriethoxysilane where R′ includes an isocyanategroup. These compounds may be used alone or in combinations of two ormore.

The trifunctional organosilane used according to the present inventionmay also be a hydrolysate of the compound represented by the generalformula R′Si(OR)₃ (where R′ is a substituted or unsubstituted alkylgroup, vinyl group, etc. and R is an alkyl group, etc.). Here, thesubstituent of R′ preferably includes an epoxy group. The same specificexemplary compounds given above apply.

The process used to obtain hydrolysates of these compounds can be aknown process involving direct addition of an acid or alkali to thetrifunctional organosilane.

The acryl polyol used according to the present invention is a polymercompound obtained by polymerizing an acrylic acid derivative monomer ora copolymer compound obtained by copolymerizing an acrylic acidderivative monomer and another monomer, the (co)polymer compound alsohaving a terminal hydroxyl group so as to react with the isocyanategroup of the isocyanate compound which is subsequently added. Among suchcompounds it is preferred to use acryl polyols obtained by simplepolymerization of acrylic acid derivative monomers such as ethyl(meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate and hydroxybutyl (meth)acrylate, or obtained bycopolymerization through addition of another monomer such as styrene.From the standpoint of reactivity with the isocyanate compound, it ispreferred for the hydroxy value to be between 5 and 200 (KOHmg/g).

The mixing ratio of the acryl polyol and the trifunctional organosilaneis preferably in the range of 1/1 to 100/1, and more preferably in therange of 2/1 to 50/1, in terms of weight ratio.

No catalyst is necessary when combining the acryl polyol with thetrifunctional organosilane when R′ in the aforementioned general formulaincludes an isocyanate group. Addition of a reaction catalyst ispreferred, however, when combining the acryl polyol with a trifunctionalorganosilane other than a trifunctional organosilane with an isocyanategroup, in order to promote the reaction. From the standpoint ofreactivity and polymerization stability, the catalyst added ispreferably a tin compound such as tin chloride (SnCl₂, SnCl₄), tinoxychloride (SnOHCl, Sn(OH)₂Cl₂), a tin alkoxide or the like. Thesecatalysts may be added directly during mixing, or they may be dissolvedin a solvent such as methanol for addition. Because the catalytic effectcannot be achieved when the amount is too large or too small, it ispreferably added in the range of from 1/10 to 1/10000, and morepreferably from 1/100 to 1/2000, as a molar ratio with respect to thetrifunctional organosilane.

The isocyanate compound used for the present invention is added for thepurpose of increasing adhesion between the substrate and the inorganicoxide vapor deposition layer by the urethane bond which results fromreaction with the acryl polyol, and it functions primarily as acrosslinking or hardening agent. Isocyanate compounds which can be usedto achieve this object include monomers such as an aromatic monomer,aliphatic monomer such as tolylene diisocyanate (TDI), diphenylmethanediisocyanate (MDI), xylene diisocyanate (XDI), hexamethylenediisocyanate (HMDI) and isophorone diisocyanate (IPDI), as well as theirpolymers and derivatives. They may be used alone or in combinations.

The mixing ratio of the acryl polyol and the isocyanate compound is notparticularly restricted, but if the isocyanate compound is deficient thehardening may not be satisfactory, and if it is excessive, blocking mayoccur creating problems for working. The mixing ratio of the acrylpolyol and the isocyanate compound is therefore preferred to be suchthat the number of isocyanate groups of the isocyanate compound is nogreater than 50 times the number of hydroxyl groups of the acryl polyol.It is more preferable for the isocyanate groups and hydroxyl groups tobe at an equivalent ratio. The mixing method may be any publicly knownone and is not particularly restricted.

For enhanced solution stability when preparing the solution of thecomposition, a metal alkoxide or its hydrolysate may be added. The metalalkoxide is a compound represented by the general formula M(OR)_(n)wherein M is a metal such as Si, Al, Ti or Zr and R is an alkyl groupsuch as CH₃ or C₂H₅. Specifically there may be mentionedtetraethoxysilane [Si(OC₂H₅)₄] and tripropoxyaluminum [Al(OC₃H₇)₃].Among these are preferred tetraethoxysilane, tripropoxyaluminum andmixtures thereof, because of their relative stability in aqueoussolvents. The method used to obtain a hydrolysate of the metal alkoxidemay involve hydrolysis with the aforementioned trifunctionalorganosilane, or the metal alkoxide hydrolysate may be added separately.

The mixing ratio of the trifunctional organosilane and the metalalkoxide is preferably in the range of a molar ratio of 10:1 to 1:10from the viewpoint of solution stability. It is more preferred for theseto be combined at an equimolar ratio.

There are no particular restrictions on the coated film of thiscomposition, and for example, a solution prepared by any of thefollowing methods may be coated onto the substrate.

1) A solution prepared by mixing the acryl polyol and isocyanatecompound with the product of prior hydrolysis reaction of thetrifunctional organosilane (where the aforementioned reaction catalystmay be used);

2) A solution prepared by mixing the acryl polyol and isocyanatecompound with the trifunctional organosilane which has undergonehydrolysis reaction with a metal alkoxide (where the aforementionedreaction catalyst may be used);

3) A solution prepared by first mixing the trifunctional organosilaneand the acryl polyol in a solvent (where the aforementioned reactioncatalyst and metal alkoxide may also be added), subjecting the mixtureto hydrolysis reaction, and then adding the isocyanate compound to theproduct thereof;

4) A solution prepared by adding the isocyanate compound to a simplemixture of the trifunctional organosilane and the acryl polyol (wherethe aforementioned reaction catalyst and metal alkoxide may also beadded).

Various additives, for example, hardening accelerators such as tertiaryamines, imidazole derivatives, carboxylic acid metal salt compounds,quaternary ammonium salts, and quaternary phosphonium salts,antioxidants such as phenol-based antioxidants, sulfur-basedantioxidants and phosphite-based antioxidants, leveling agents, flowadjustors, catalysts, crosslinking reaction accelerators, fillers andthe like may also be included depending on the need.

The solvent or dilution solvent in the solution used to form the primerlayer is not particularly restricted so long as it is capable ofdissolving or diluting each of the components forming the primer layer.For example, when a trifunctional organosilane is used, an ester such asethyl acetate or butyl acetate is appropriate, and when a trifunctionalorganosilane hydrolysate is used, a mixed solvent of an ester with analcohol such as methanol, ethanol or isopropyl alcohol is appropriate.In addition to these solvents, ketones such as methyl ethyl ketone andaromatic hydrocarbons such as toluene and xylene may also be used aloneor in any desired combination. In particular, since aqueous solutions ofhydrochloric acid and the like are sometimes used for hydrolysis oftrifunctional organosilanes, it is important to use a mixed solvent ofthe polar solvent such as ethyl acetate in admixture with isopropylalcohol or the like as a co-solvent.

The thickness of the primer layer is not particularly restricted as longas a uniform coated film is formed. However, the dry film thickness(solid portion) is generally preferred to be in the range of 0.01˜2 μm.If the thickness is less than 0.01 μm it becomes difficult to obtain auniform coated film, and the adhesion will sometimes be reduced. If thethickness exceeds 2 μm, it becomes impossible to maintain flexibility ofthe coated film because of its thickness, while the risk of cracking ofthe coated film due to external factors also becomes a concern. Aparticularly preferred range for the thickness of the primer layer isfrom 0.05˜0.5 μm.

The method used to form the primer layer may be, for example, a wellknown printing process such as offset printing, gravure printing, silkscreen printing, etc. or a well known application process such as rollcoating, knife edge coating, gravure coating, etc. The drying conditionsmay be such conditions as are commonly employed.

The inorganic oxide vapor deposition layer is a vapor deposition layerof an inorganic oxide comprising aluminum oxide, silicon oxide, tinoxide, magnesium oxide or a mixture thereof. The layer should betransparent and have gas barrier properties against oxygen, water vapor,etc. Particularly preferred among these are aluminum oxide and siliconoxide. However, the vapor deposition layer of the present invention isnot limited to the above-mentioned inorganic oxides, and any othermaterial may be used which meets the aforementioned requirements.

The optimum thickness of the vapor deposition layer will depend on thetype and structure of the inorganic oxide used, but it is generallypreferred to be appropriately selected within a range of 5˜300 nm. Ifthe film thickness is less than 5 nm it may not be possible to obtain auniform film and the film thickness may be inadequate, which may preventit from adequately carrying out its function as a gas barrier material.If the film thickness is over 300 nm, it becomes impossible to maintainflexibility of the thin-film, presenting the risk of cracking of thethin-film due to external factors such as bending and stretching afterformation of the film. A preferred range for the thickness of the vapordeposition layer is from 10 to 150 nm.

Many different methods exist for formation of the inorganic oxide vapordeposition layer on the primer layer, and common vacuum vapor depositionmay be employed. Other thin-film forming methods, such as sputtering,ion plating and plasma vapor phase growth methods (CVD) may also beused. From the standpoint of productivity, however, vacuum vapordeposition is a superior method at the current time. The heating meansused for vacuum vapor deposition is preferably an electron beam heatingsystem, resistance heating system or induction heating system. Forbetter adhesion between the vapor deposition layer and the substrate andgreater density of the vapor deposition layer, the vapor deposition maybe accomplished by the plasma assist method or ion beam assist method.For higher transparency of the vapor deposition film, the vapordeposition reaction may be carried out while blowing in oxygen gas orthe like.

An overcoating layer is optionally formed on the inorganic oxide vapordeposition layer in order to provide higher gas barrier propertiesdepending on the quality demanded.

The overcoating layer is formed using a coating agent composed mainly ofan aqueous solution or aqueous/alcohol mixed solution which contains anwater-soluble polymer and either or both (a) at least one metal alkoxideor hydrolysate thereof and (b) tin chloride. This may be, for example, asolution prepared by dissolving the water-soluble polymer and tinchloride in an aqueous (water or water/alcohol mixture) solvent, or sucha solution modified by mixture with a metal alkoxide directly or afterits hydrolysis or other treatment. After coating of the solution ontothe inorganic oxide vapor deposition layer, it is heated and dried toform the layer. The various components included in the coating agentwill now be described in further detail.

As water-soluble polymers to be used in the coating agent according tothe present invention there may be mentioned polyvinyl alcohol,polyvinylpyrrolidone, starch, methyl cellulose, carboxymethyl cellulose,sodium alginate, etc. Polyvinyl alcohol (hereunder, simply called asPVA) in particular has the most excellent gas barrier property when usedin the coating agent of the present invention. PVA is generally obtainedby saponification of polyvinyl acetate. The PVA is not particularlyrestricted and includes, for example, partially saponified PVA wherein10%, 20% or more of the acetate groups remain, or total PVA wherein onlya few percent of the acetate groups remain.

The tin chloride used in the coating agent may be stannous chloride(SnCl₂), stannic chloride (SnCl₄) or a mixture thereof. These tinchloride compounds may be anhydrates or hydrates.

The metal alkoxide is a compound represented by the general formulaM(OR)_(n) wherein M is a metal such as Si, Ti, Al or Zr and R is analkyl group such as CH₃ or C₂H₅. Specifically there may be mentionedtetraethoxysilane [Si(OC₂H₇)₄] and triisopropoxyaluminum[Al(O-2′-C₃H₅)₃], tetraethoxysilane and triisopropoxyaluminum beingpreferred because of their relative stability in aqueous solvents afterhydrolysis.

If necessary, a publicly known additive such as an isocyanate compoundor silane coupling agent or a dispersing agent, stabilizer, viscosityadjustor, coloring agent or the like, may be added to an extent whichdoes not impair the gas barrier properties of the coating agent.

Preferred examples of isocyanate compounds which may be added to thecoating agent include ones having two or more isocyanate groups in themolecule. For example, there may be mentioned tolylene diisocyanate,triphenylmethane triisocyanate, tetramethylxylene diisocyanate and othersuch monomers, as well as their polymers and derivatives.

The method for applying the coating agent may employ a publicly knownmeans for commonly used dipping methods, roll coating methods, screenprinting methods, spray methods and the like. The thickness of thecoated film will differ depending on the type of coating agent and theworking conditions; the post-drying thickness may be 0.01 μm or greater,but if the thickness exceeds 50 μm cracks will tend to occur in thefilm, and therefore the range of 0.01˜50 μm is preferred.

Other layers may also be laminated over the inorganic oxide vapordeposition layer or the overcoating layer. Examples thereof includeprinted layers, interlayer films, heat seal layers, etc.

A printed layer is formed for practical application as a packaging bagor the like. It is, for example, a layer composed of an ink prepared byadding an additive such as any of various pigments, extender pigments,plasticizers, desiccators, stabilizers and the like, to a conventionallyemployed ink binder resin which is urethane-based, acrylic-based,nitrocellulose-based, rubber-based, vinyl chloride-based, etc. Theprinting forms characters, images and the like. The forming process maybe a well known printing process such as offset printing, gravureprinting or silk screen printing, or a well known application processsuch as roll coating, knife edge coating or gravure coating. The dryfilm thickness (solid portion) of the printed layer may be from 0.1 to2.0 μm.

An interlayer film is formed between the vapor deposition layer orovercoating layer and the heat seal layer in order to increase therupture strength during boiling or retort sterilization, and from thestandpoint of mechanical strength and thermal stability, generally itmust be of a type selected from among biaxially stretched nylon films,biaxially stretched polyethylene terephthalate films and biaxiallystretched polypropylene films. Its thickness will be determined based onthe material and the demanded quality, but it is generally in the rangeof 10˜30 μm. The method of lamination may be a publicly known one suchas dry lamination involving attachment using an adhesive agent such as atwo-part curing type urethane-based resin.

A heat seal layer is provided as an adhesive layer when forming bag-likepackages. Examples of resins which may be used or the heat seal layerinclude polyethylene, polypropylene, ethylene-vinyl acetate copolymer,ethylene-methacrylic acid copolymer, ethylene-methacrylic acid estercopolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid estercopolymer, and metal crosslinked forms thereof. The thickness will bedetermined based on the purpose, but it is generally in the range of15˜200 μm. The method of lamination will generally be a method such asdry lamination involving attachment of a film of the resin using anadhesive agent such as a two-part curing type urethane-based resin, butother publicly known methods may be used for the lamination.

A packaging material employing a vapor deposition film according to thepresent invention can be used as a packaging material in the field offoods, non-foods and medicines. In particular, when it is used as apackaging material for boiling sterilization, retort sterilization orautoclave sterilization, it gives a packaging material with excellenttransparency and gas barrier properties while also avoiding the problemof peeling, etc.

Any form of packaging is possible as a packaging employing the packagingmaterial of the invention, and as examples there may be mentionedthree-side sealed pouches, four-side sealed pouches, standing typepouches, pillow type pouches and the like. The packaging may also be ina form with a cover sealing the opening of an open container. A publiclyknown method may be used as the shaping method.

FIG. 3 is a cross-sectional view of the layer structure of a packagingmaterial according to an embodiment of the invention. In this drawing,reference numeral 1 denotes a substrate, 2 a primer layer, 3 a vapordeposition layer, 4 an overcoating layer, 5 an adhesive layer, 6 aninterlayer film, 7 another adhesive layer and 8 a heat seal layer. Theheat seal layers of packaging materials constructed in this fashion areattached together and heat sealed, to form a standing type pouch such asshown in FIG. 4, for example.

EXAMPLES

A packaging material employing the vapor deposition film of the presentinvention will now be further explained with reference to concreteexamples, with the understanding that the invention is not limited tothese examples so long as the gist thereof is maintained.

(Preparation of Primer Layer Solution)

A) In a diluting solvent (ethyl acetate) 2-(epoxycyclohexyl)ethyltrimethylsilane (hereunder, simply called as EETMS) and acryl polyol ata 5.0-fold amount (weight ratio) with respect to the EETMS were mixed. Atin chloride (SnCl₂)/methanol solution (prepared to 0.003 mol/g) wasfurther added to the mixture as a catalyst to 1/135 mol with respect tothe EETMS, and the mixture was stirred. Tolylene diisocyanate(hereunder, simply called as TDI) was then added at an equivalent ofisocyanate groups in the TDI with respect to hydroxyl groups in theacryl polyol. The mixed solution was diluted to 2% by weight as a totalconcentration of the added components to make solution A.

B) In a diluting solvent (isopropyl alcohol/ethyl acetate) EETMS andtetraethoxysilane (Si(OC₂H₅)₄: hereunder, simply called as TEOS) weremixed at a molar ratio of 1:1. To this mixture there were added acrylpolyol at a 2.5-fold amount in terms of weight and a tin chloride(SnCl₂)/methanol solution (prepared to 0.003 mol/g) as a catalyst at anamount of 1/400 mol with respect to the mixture, and the mixture wasstirred. Next, 0.1 N hydrochloric acid was added and stirred therewithfor hydrolysis. TDI was then added at an equivalent of isocyanate groupsin the TDI with respect to hydroxyl groups in the acryl polyol. Themixed solution was diluted to 2% by weight as a total concentration ofthe added components to make solution B.

C) In a diluting solvent (isopropyl alcohol/ethyl acetate) EETMS andTEOS were mixed at a molar ratio of 1:1. To this mixture there was addedacryl polyol at a 2.5-fold amount in terms of weight. TDI was then addedat an equivalent of isocyanate groups in the TDI with respect tohydroxyl groups in the acryl polyol. The mixed solution was diluted to2% by weight as a total concentration of the added components to makesolution C.

D) In a diluting solvent (ethyl acetate), TDI was added as an isocyanatecompound to acryl polyol at an equivalent of isocyanate groups in theTDI with respect to hydroxyl groups in the acryl polyol. The mixedsolution was diluted to 2% by weight as a total concentration of theadded components to make solution D.

E) In a diluting solvent (ethyl acetate), 5 parts by weight of acrylpolyol was mixed with 1 part by weight of γ-isocyanatepropyltrimethoxysilane, and the mixture was stirred. TDI was then addedas an isocyanate compound at an equivalent of isocyanate groups in theTDI with respect to hydroxyl groups in the acryl polyol. The mixedsolution was diluted to 2% by weight as a total concentration of theadded components to make solution E.

F) In a diluting solvent (ethyl acetate), 5 parts by weight of acrylpolyol was mixed with 1 part by weight of γ-isocyanatepropyltrimethoxysilane, and the mixture was stirred. XDI was then addedas an isocyanate compound at an equivalent of isocyanate groups withrespect to hydroxyl groups in the acryl polyol. The mixed solution wasdiluted to 2% by weight as a total concentration of the added componentsto make solution F.

G) In a diluting solvent (ethyl acetate), 5 parts by weight of acrylpolyol was mixed with 1 part by weight of -isocyanatepropyltrimethoxysilane, and the mixture was stirred. A 7:3 mixture ofXDI and IPDI as isocyanate compounds was then added at an equivalent ofisocyanate groups in the isocyanate compound mixture with respect tohydroxyl groups in the acryl polyol. The mixed solution was diluted to2% by weight as a total concentration of the added components to makesolution G.

Example 1

On one side of a 12-μm thick biaxially stretched polyethyleneterephthalate (PET) film as the substrate 1, the solution A was coatedand dried by gravure coating to a dry film thickness of 0.2 μm, to forma primer layer 2. An electron beam heating-type vacuum vapor depositionapparatus was then used for vaporization of metallic aluminum, andoxygen gas was introduced therein to form an aluminum oxide vapordeposition layer 3 to a thickness of 20 nm on the primer layer 2. Acoating agent with the composition described below was further coatedthereon by gravure coating. After coating, it was dried at 120° C. forone minute to form a 0.3-μm thick overcoating layer 4, thus yielding avapor deposition film. Composition of coating agent: Mixture of solution(1) and solution (2) below at a mixing ratio (wt %/wt %) of 60/40.

Solution (1): Hydrolyzed solution with solid portion of 3 wt % (as SiO,)prepared by adding 89.6 g of hydrochloric acid (0.1 N) to 10.4 g oftetraethoxysilane and stirring for 30 minutes for hydrolysis.

Solution (2): Water/isopropyl alcohol solution (water:isopropyl alcoholweight ratio=90:10) containing 3 wt % polyvinyl alcohol.

The overcoating layer 4 of the resulting vapor deposition film waslaminated with a biaxially stretched nylon film with a thickness of 15μm as an interlayer film 6 by dry lamination, via a two-part curing typeurethane-based adhesive, and then a 70-μm thick polypropylene film waslaminated as a heat seal layer 8 by dry lamination via a two-part curingtype urethane-based adhesive, to fabricate a packaging material.

Example 2

A packaging material was obtained in the same manner as Example 1,except that the vapor deposition layer 3 in Example 1 consisted ofsilicon oxide at a thickness of about 40 nm obtained by vacuum vapordeposition with a resistance heating system.

Example 3

A packaging material was obtained in the same manner as Example 1,except that the solution B was used as the primer layer 2 in Example 1.

Example 4

A packaging material was obtained in the same manner as Example 1,except that the solution C was used as the primer layer 2 in Example 1.

Example 5

A packaging material was obtained in the same manner as Example 1,except that the solution E was used as the primer layer 2 in Example 1.

Example 6

A packaging material was obtained in the same manner as Example 1,except that the solution F was used as the primer layer 2 in Example 1.

Example 7

A packaging material was obtained in the same manner as Example 1,except that the solution G was used as the primer layer 2 in Example 1.

Comparative Example 1

A packaging material was obtained in the same manner as Example 1,except that the primer layer 2 in Example 1 was not formed.

Comparative Example 2

A packaging material was obtained in the same manner as Example 1,except that the solution D was used as the primer layer in Example 1.

(Test 1)

The packaging materials of the present invention according to Examples1-7 and the packaging materials according to Comparative Examples 1-2which were fabricated in the manner described above were used to makepouches with the 4 sides as the sealing portions, and each was filledwith 150 g of water as the contents. Retort sterilization was thencarried out at 121° C. for 30 minutes. The evaluation was based on theoxygen permeability before and after the retort sterilization (using anoxygen permeation measuring apparatus (OXTRAN-10/50A by Modern ControlCo.) for measurement in an atmosphere of 30° C., 70%RH, units:cc/m²/day), the laminate strength (measured by peel rate at 300 mm/min,units: gr/15 mm) and the visually observed state of peeling between thesubstrate and the vapor deposition layer after retort sterilization. Thestate of peeling was determined by observing the peeling of the vapordeposition layer upon 180-degree bending of the pouch seal sectionsafter retort sterilization. The results are listed in Table 1.

The symbols used in Table 1 to indicate the evaluation results for theappearance of peeling after retort sterilization are as follows.

⊚: No peeling

×: Peeling

The symbols used in Table 1 for the overall evaluation results are asfollows.

⊚: Good

×: Unusable

TABLE 1 Oxygen permeability Laminate strength Appearance Before retortAfter retort Before retort After retort after retort Overallsterilization sterilization sterilization sterilization sterilizationevaluation Example 1 0.34 0.52 580 580 ⊚ ⊚ Example 2 0.41 0.43 570 510 ⊚⊚ Example 3 0.38 0.47 450 420 ⊚ ⊚ Example 4 0.51 0.48 500 450 ⊚ ⊚Example 5 0.69 0.80 590 330 ⊚ ⊚ Example 6 0.63 0.77 540 340 ⊚ ⊚ Example7 0.72 0.81 630 350 ⊚ ⊚ Comp. Ex. 1 0.34 1.08 460 100 × × Comp. Ex. 20.42 0.74 540 300 × ×

Table 1 shows that the vapor deposition films of the present inventionaccording to Examples 1-7 and the packaging materials employing themhave sufficient transparency to allow direct viewing of their contents.The examples of the present invention have high gas barrier propertiesto block gases which can affect the contents, as well as high laminatestrength. Even after retort sterilization there is no deterioration ofthe gas barrier properties, and the high laminate strength ismaintained. They clearly exhibit excellent retort sterilizationresistance with no peeling of their vapor deposition layers.

In comparison, the packaging materials of Comparative Examples 1 and 2also have sufficient transparency to allow direct viewing of thecontents, and prior to retort sterilization they had high gas barrierproperties to block gases which can affect the contents, as well as highlaminate strength. After retort sterilization, however, it is seen thatthe gas barrier properties of the packages deteriorated, the laminatestrength was lowered, peeling occurred, and the retort sterilizationresistance was poor.

Example 8

On one side of a 12-μm thick biaxially stretched polyethyleneterephthalate (PET) film as the substrate 1, the solution E was coatedby gravure coating and dried to a dry film thickness of 0.2 μm, to forma primer layer 2. An electron beam heating-type vacuum vapor depositionapparatus was then used for vaporization of metallic aluminum, andoxygen gas was introduced therein to form an aluminum oxide vapordeposition layer 3 to a thickness of 20 nm on the primer layer 2.

A 30-μm thick polypropylene film was laminated as a heat seal layer onthe resulting vapor deposition layer 3 by dry lamination via a two-partcuring type urethane-based adhesive, to fabricate a packaging material.

Comparative Example 3

A packaging material was obtained in the same manner as Example 8,except that the primer layer 2 in Example 8 was not formed.

(Test 2)

The packaging material of the present invention according to Example 8and the packaging material according to Comparative Example 3 which werefabricated in the manner described above were used for measurement ofthe laminate strength between the vapor deposition layer and the heatseal layer (measured at a peel rate of 300 mm/min, units: gr/15 mm). Thelaminate strength was also measured in a similar manner while running asmall amount of tap water over the peeling surface between the vapordeposition layer and the heat seal layer. The results are listed inTable 2.

TABLE 2 Laminate strength Without running water With running waterExample 8 640 540 Comp. Ex .3 660   50

As is clear from the explanation given above, vapor deposition filmsaccording to the present invention and packaging materials employingthem have a construction wherein formation of a primer layer withexcellent dimensional stability and adhesion even after boilingsterilization or retort sterilization on a transparent plastic substrateis followed by lamination of a vapor deposition layer made of aninorganic oxide with excellent gas barrier properties. They thereforehave transparency which allows their contents to be directly viewed, aswell as high gas barrier properties comparable to those of aluminumfoil. In addition, there is no peeling or loss of gas barrier propertiesof the vapor deposition layer even after boiling sterilization or retortsterilization. Thus, they have a wide range of possible uses in thefield of packaging, as packaging materials for common foods, non-foods,medicines and the like.

While the presently preferred embodiments of the present invention havebeen shown and described, it will be understood that the presentinvention is not limited thereto, and that various changes andmodifications may be made by those skilled in the art without departingfrom the scope of the invention as set forth in the appended claims.

What is claimed is:
 1. A vapor deposition film comprising: a substratemade of a plastic material, a primer layer comprising: a trifunctionalorganosilane represented by the general formula R′Si(OR)₃ wherein R′ isa substituted or unsubstituted alkyl group or a vinyl group, and R is analkyl group, an acryl polyol, and an isocyanate compound, and a vapordeposition layer comprising an inorganic oxide formed to a thickness of5˜300 nm, the primer layer and the vapor deposition layer being formedby successive lamination on at least one side of said substrate.
 2. Avapor deposition film according to claim 1, wherein R′ in the structureof said trifunctional organosilane is an alkyl group including an epoxygroup.
 3. A vapor deposition film according to claim 1, wherein areaction catalyst is added to said composition.
 4. A vapor depositionfilm according to claim 3, wherein said reaction catalyst is a tincompound.
 5. A vapor deposition film according to claim 4, wherein saidtin compound is a tin compound selected from the group consisting of tinchloride, tin oxychloride and tin alkoxides.
 6. A vapor deposition filmaccording to claim 1, wherein R′ in the structure of said trifunctionalorganosilane is an alkyl group including an isocyanate group.
 7. A vapordeposition film according to claim 1, wherein a metal alkoxiderepresented by the general formula M(OR)_(n) (wherein M is a metalelement, R is an alkyl group such as CH₃, C₂H₅, etc. and n is theoxidation number of the metal element) or a hydrolysate of said metalalkoxide is further added to said composition.
 8. A vapor depositionfilm according to claim 7, wherein the metal of said metal alkoxide is ametal selected from the group consisting of Si, Al, Ti, Zr and theirmixtures.
 9. A vapor deposition film comprising: a substrate made of aplastic material, a primer layer comprising: a hydrolysate of atrifunctional organosilane represented by the general formula R′Si(OR)₃wherein R′ is a substituted or unsubstituted alkyl group or a vinylgroup, and R is an alkyl group, an acryl polyol and an isocyanatecompound, and a vapor deposition layer comprising an inorganic oxideformed to a thickness of 5˜300 nm, the primer layer and the vapordeposition layer being formed by successive lamination on at least oneside of said substrate.
 10. A vapor deposition film according to claim9, wherein R′ in the structure of said trifunctional organosilane is analkyl group including an epoxy group.
 11. A vapor deposition filmaccording to claim 9, wherein a reaction catalyst is added to saidcomposition.
 12. A vapor deposition film according to claim 11, whereinsaid reaction catalyst is a tin compound.
 13. A vapor deposition filmaccording to claim 12, wherein said tin compound is a tin compoundselected from the group consisting of tin chloride, tin oxychloride andtin alkoxides.
 14. A vapor deposition film according to claim 9, whereina metal alkoxide represented by the general formula M(OR)_(n) (where Mis a metal element, R is an alkyl group such as CH₃, C₂H₅, etc. and n isthe oxidation number of the metal element) or a hydrolysate of saidmetal alkoxide is further added to said composition.
 15. A vapordeposition film according to claim 14, wherein the metal of said metalalkoxide is a metal selected from the group consisting of Si, Al, Ti, Zrand their mixtures.
 16. A vapor deposition film according to claim 1,wherein the thickness of said primer layer is in the range of 0.01˜2 μm.17. A vapor deposition film according to claim 1, wherein said inorganicoxide is one selected from the group consisting of aluminum oxide,silicon oxide, magnesium oxide and their mixtures.
 18. A vapordeposition film according to claim 1, wherein an overcoating layer isadditionally laminated on said vapor deposition film, said overcoatinglayer being a layer obtained by applying, heating and drying a coatingagent composed mainly of an aqueous solution or an aqueous/alcohol mixedsolution containing a water-soluble polymer and either or both (a) atleast one metal alkoxide or hydrolysate thereof and (b) tin chloride.19. A vapor deposition film according to claim 18, wherein said metalalkoxide is one selected from the group consisting of tetraethoxysilane,triisopropoxyaluminum and mixtures thereof.
 20. A vapor deposition filmaccording to claim 1, wherein said water-soluble polymer is polyvinylalcohol.
 21. A packaging material comprising a vapor deposition filmaccording to claim 1, and a heat seal layer laminated on the vapordeposition layer or overcoating layer side thereof.
 22. A package formedinto a bag using a packaging material according to claim
 21. 23. A vapordeposition film according to claim 19, wherein said water-solublepolymer is polyvinyl alcohol.
 24. A vapor deposition film according toclaim 1, wherein a number of isocyanate groups in the trifunctionalorganosilane is no greater than 50 times the number of hydroxyl groupsof the acryl polyol.
 25. A vapor deposition film according to claim 9,wherein a number of isocyanate groups in the trifunctional organosilaneis no greater than 50 times the number of hydroxyl groups of the acrylpolyol.
 26. A vapor deposition film according to claim 7, wherein amolar ratio of the trifunctional organosilane to the metal alkoxide isin the range of 10:1 to 1:10.
 27. A vapor deposition film according toclaim 14, wherein a molar ratio of the trifunctional organosilane to themetal alkoxide is in the range of 10:1 to 1:10.
 28. A vapor depositionfilm according to claim 7, wherein a molar ratio of the trifunctionalorganosilane to the metal alkoxide is in the range of an equimolarratio.
 29. A vapor deposition film according to claim 14, wherein amolar ratio of the trifunctional organosilane to the metal alkoxide isin the range of an equimolar ratio.